Why kill the Potters?

[BoBaFeTT]

No: HPFGUIDX 52372

Why is it that the Potters had to die anyway?

Prof Dumbledore stated if Harry had witnessed Prof. Trelawney's truly predicting the future then that would make 2 times she had done it.
I'm thinking that the first prediction came a while back and that she predicted the death of Voldemort, at the hands of a Potter Man. Seeing as Harry and his father were the last men of the Potter family killing them would end any chance of the prediction coming true. 

That brings up the question of who was the person who witnessed her prediction. When Harry saw her do it she had no memory of it. Perhaps it was during a class and Lucius Malfoy was in the class or somthing like that.

-BoBaFeTT

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